University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 1/21 Orbit Correction Within Constrained Solution Spaces

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 2/ GeV, 115m circ., 8-6h (vacuum!), ~6nm rad 1.5 GeV, 115m circ., 8-6h (vacuum!), ~6nm rad full energy booster ~6.5secs, 3000 h/y uptime full energy booster ~6.5secs, 3000 h/y uptime 3IDs: U250 (FEL), SAW (5.5T), U55 3IDs: U250 (FEL), SAW (5.5T), U55 54 RF-BPMs resolving: 5µm relative (12bit ADC limited) ~100µm absolut (calibration)... within ±10mm 30 horizontal correctors 26 vertical correctors

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 3/21 Constraints for Orbit Correction i. Hardware limitation of physical corrector strengths – Global orbit correction on a misaligend (low emittance) magnet lattice – Local orbit bumps of increased amplitude (aperture scans, BBC, etc) – Enhanced by: Little maximum corrector strengths Little Phase advances (low tune) Calibrational errors of BPM offsets ii. Solution space of local impact (bumps) iii. Exploitation of nullspace

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 4/21 DELTA Corrector Design Corrector Coils Magnetic Field Resulting Deflection Electron Beam

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 5/21 horizontal correctors: long yoke (40cm): 2x150 windings max: GeV short yoke (20cm): 2x240 windings max: GeV vertical correctors: short yokes only: 4x50 windings max: 1.1 – GeV Corrector Strength ±10A max!

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 6/21 Constraints for Orbit Correction i. Hardware limitation of physical corrector strengths – Global orbit correction on a misaligend (low emittance) magnet lattice – Local orbit bumps of increased amplitude (aperture scans, BBC, etc) – Enhanced by: Little maximum corrector strengths Little phase advances (low tune) Calibrational errors of BPM offsets ii. Solution space of local impact (bumps) iii. Exploitation of nullspace

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 7/21 Phase advance between neighbouring BPMs [  ] Highly sensitive to calibration! Total Phase Advance [2  ] Vertical BPM Phase Advances at DELTA

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 8/21 Significance of Calibration Errors Correction of simulated offsets for: bpm µm bpm µm vertical Displacement [mm] Large corrector strengths afforded (>0.5 out of 0.5 to 1.1 mrad max) Error propagatation (1.2mm !!)

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 9/21 Constraints for Orbit Correction i. Hardware limitation of physical corrector strengths – Global orbit correction on a misaligend (low emittance) magnet lattice – Local orbit bumps of increased amplitude (aperture scans, BBC, etc) – Enhanced by: Little maximum corrector strengths Little phase advances (low tune) Calibrational errors of BPM offsets ii. Solution space of local impact (bumps) iii. Exploitation of nullspace

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 10/21 SVD-Based Orbit Correction Inverse within the Range of WR (Pseudoinverse):

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 11/21 DOF* for Correction Free Parameter for SVD-Based matrix inversion: DOF* for correction ii *DOF= Degrees Of Freedom

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 12/21 Relative corrector strength -100% prediction +100% Solutions for Constraining Correctors ? rather ficticious task here typical for DELTA about 2 limited correctors vertically (usually no problems horizontally)

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 13/21 Weighted Orbit Space Corrector Space intermingled nullspace Weighted Orbit Space orthogonal nullspace  Find the closest spot to a given point on a set of hyperplanes in n dimensions  Restrict solution space to the „Range“  n-dimensional solving strategies...  KKT criterion to identify unique solution  Find the closest spot to a given point on a set of hyperplanes in n dimensions  Restrict solution space to the „Range“  n-dimensional solving strategies...  KKT criterion to identify unique solution

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 14/21 ! Numbers scale with weights ! limiting

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 15/21 No correction DOF for correction better # of limiting correctors worse Residual orbit deviation Quality of correction Test of Code Integrity ‚suboptimal‘ strategy

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 16/21 Constraints for Local Orbit Bumps Locality = minimise orbit impact ouside bump (ROI) – Choose correctors k surrounding bump monitors  H ={k} – Zero out lines of monitors between correctors H – SVD of yields 2 large singular values (SVs) –| H |-2 column vectors of corresponding to remaining SVs constitute ON-Basis for local orbit bumps (minimum impact outside ROI)  Solve... under restriction of the solution space to  Solve... under restriction of the solution space to

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 17/21 Local Orbit Bumps (Example) -1mm orbit Dynamically choose as many correctors as needed Produce asked orbit offset ‚without concern‘ of corr. lims. Provided as agent service to external clients 100%

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 18/21 Exploitation of Nullspace (i) Use little orbit impact of ON-Base to ease large corrector strengths in current setting :  find such as to minimise with diagonal corrector weight matrix  choose large weights to put an emphasis on correctors j to be eased

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 19/21 Exploitation of Nullspace (ii)... again, use SVD to create a weighted ON-Base of correctors:  Solve... under restriction of the solution space to  Solve... under restriction of the solution space to

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 20/21 Bottom Line SVD based orbit correction restricted to the common set of feasable corrector strengths Flexibility („no matter“ what the offsets and limits are) Effectivity (!?) (still an idea, usefulness to be proven) + Restriction to local orbit bumps + Restriction to Nullspace Reliability!! (while retaining the best solution possible) operational since 4/2004

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 21/21 Thanks for your attention

University of Dortmund Marc Grewe, IWBS 2004, Grindelwald, CH 22/21 Monitor Positioning